Added 'Even Fibonacci' solution

.gitignore

@@ -1 +1,2 @@
 mult3or5/main
+evenFibonacci/main

README.md

@@ -0,0 +1,5 @@
+## Project Euler Solutions
+
+This repository contains my solutions to the [Project Euler problems](https://projecteuler.net/archives), written - to the best of my abilities - in 32-bit ARM Assembly.
+
+The Assembly code was written and tested on a Raspberry Pi 3B, and contains C code to facilitate formatted input and output.

evenFibonacci/README.md

@@ -0,0 +1,3 @@
+## Multiples of 3 or 5
+
+This directory contains my solution to the ['Even Fibonacci numbers' problem](https://projecteuler.net/problem=2).

evenFibonacci/main.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+int evenFib();
+
+void main() {
+	printf("%d\n",evenFib());
+	return;
+}

evenFibonacci/main.s

@@ -0,0 +1,35 @@
+.global evenFib
+
+.section .text
+evenFib:
+init:
+	PUSH {R4}		@The ARM calling convention only allows callee functions to use R0-R3. Since I need R4 as well, I am going to push R4 onto the stack, and pop it off when I am done using it.
+	MOV R0,#0		@Return value - where all the addition is going to happen to
+	LDR R4,=#4000000	@ARM doesn't allow you to 'MOV' constants greater than 8 bits. To get around that, we use the LDR instruction, which lets the assembler place the value in memory, and then load it from there.
+	MOV R1,#1		@Main fibonacci number
+	MOV R2,#0		@Used to hold temporary values when incrementing the main fibonacci number
+	MOV R3,#0		@Previous fibonacci number - This will be 0 at the start
+loop:
+
+incr:
+	MOV R2,R1	@Store the current fibonacci number in R2
+	ADD R1,R1,R3	@Add the previous fibonacci number with the current one
+	MOV R3,R2	@Move R2 (the 'old current' fibonacci number) into R3
+checkbnd:
+	CMP R1,R4	@Check if R1 is greater than the upper bound for fibonacci numbers
+	BGE return	@If it is, then we return
+
+checkparity:		@Parity - The fact of being even or odd.
+	TST R1,#0x1	@Equivalent of an ANDS operation, but the result is discarded. In this case, we are checking if R1's parity by checking the last bit, which would be set to 0 if it is even, and 1 if it is odd.
+	BNE loop	@If R1 is odd, don't do the addition. Instead, go back to the loop, where we move on to the next fibonacci number.
+
+
+isEven: @The program goes here if R1 is even
+	ADD R0,R0,R1	@Add the fibonacci number to R0
+	B loop
+
+return:
+	POP {R4}	@Pop the R4 that we pushed onto the stack earlier
+	BX lr
+
+.section .data

mult3or5/README.md

@@ -0,0 +1,3 @@
+## Multiples of 3 or 5
+
+This directory contains my solution to the ['Multiples of 3 or 5' problem](https://projecteuler.net/problem=1).

mult3or5/main.s

@@ -2,9 +2,11 @@
 .section .text
 
 func:
+init:
 	MOV R0,#3  @Move 3 to R0
 	MOV R1,#5  @Move 5 to R1
 	MOV R2,#0  @Move 0 to R2
+	MOV R3,#1000  @The value to compare with
 loop:
 add5:
 	ADD R2,R2,R1  @Add R1 to R2
@@ -14,21 +16,20 @@ add3:
 	ADD R0,R0,#3  @Increment R0 by 3
 
 check3:
-	CMP R0,#1000  @Is R0 less than 1000?
-	BLT check5  @If true, check 5
+	CMP R0,R3  @Is R0 less than 1000?
 	BGE rmv15  @If the multiple of 3 is greater than 1000, go to rmv15
 
 check5:
-	CMP R1,#1000  @Is R1 less than 1000?
+	CMP R1,R3  @Is R1 less than 1000?
 	BLT loop  @If true, go back to loop
-	BGE add3  @If the multiple of 5 reaches 1000, go to add3 - Continue adding multiples of 3, because those wouldn't have reached 1000 yet
+	BGE add3  @If the multiple of 5 reaches 1000, go back to add3 instead of loop - Continue adding multiples of 3, because those wouldn't have reached 1000 yet
 
 rmv15:
-	MOV R0,#15  @The loop that follows is intended to subtract multiples of 15, which would have been added twice - 3, 6, 9, 12, 15, 18 ; 5, 10, 15, 20
+	MOV R0,#15  @The loop that follows is intended to subtract multiples of 15, which would have been added twice - 3, 6, 9, 12, [15], 18 ; 5, 10, [15], 20
 loop2:
 	SUB R2,R2,R0
 	ADD R0,R0,#15
-	CMP R0,#1000
+	CMP R0,R3
 	BLT loop2